High aspect ratios and the rigid structure of oxide nanowires (NWs) make them useful for nanoscale circuits, interconnects, NEMs, and chemical sensing. There is significant worldwide interest in ZnO NWs primarily due to there ease of synthesis by CVD. Critical to their application is the location and diameter control of these 1-D nanostructures. Our research focuses on the growth of ZnO NWs from an exposed edge of a Si/Al2O3 (10-30 nm)/Si thin film multilayer structure patterned on a silicon substrate. The Al2O3 film acts as a nucleation site for ZnO NW growth, where film thickness controls the diameter of resulting nanowire at the edge of the pattern. Taking advantage of the exposed face of the edge of a trilayer pattern eliminates the necessity for e-beam lithography as the film thickness determines nm-scale line dimension. A variety of material pairs for capping/nucleation layers were examined with Si/Al2O3/Si the most promising. ZnO nanowire growth is performed at 700o C in a high temperature 2-zone furnace with an Ar flow of 130-150 sccm and O2 flow of 8-10 sccm. The vapor pressure of the metallic Zinc source is controlled by the flow of gases and the source zone temperature. ZnO NWs were observed to grow from the cleaved/etched face of the multilayer structure in the selective area. The NWs exhibited diameters between 20 to 40 nm and an aspect ratio over 20. The NWs were characterized by SEM, TEM and EDS studies. The diameter of ZnO nanowires can be adjusted by changing the thickness of Al2O3 thin film. Such an approach to control nanowire diameter and its selective growth can be the basis for the development of bottom-up growth of architectures and cast nm-scale lines in a shadow lithography process.